CN106471146B

CN106471146B - Steel wire wire rod and steel wire

Info

Publication number: CN106471146B
Application number: CN201580034206.9A
Authority: CN
Inventors: 石田友信; 增田智; 增田智一
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2014-07-01
Filing date: 2015-06-02
Publication date: 2018-03-16
Anticipated expiration: 2035-06-02
Also published as: CN106471146A; MX2016017015A; EP3165623A1; JP2016014169A; CA2951781A1; WO2016002414A1; EP3165623A4; US20170130303A1; KR20170012467A

Abstract

There is provided that a kind of low cycle fatigue property is excellent, the useful steel wire wire rod of the former material as the steel wire of the high intensity of steel wire rope and PC steel wires etc., and the steel wire of such characteristic can be played.The steel wire wire rod of the present invention, in terms of quality %, contains C respectively：0.70~1.3%, Si：0.1~1.5%, Mn：0.1~1.5%, N：0.001~0.006%, Al：0.001~0.10%, Ti：0.02~0.20%, B：0.0005~0.010%, P：More than 0% and less than 0.030%, S：More than 0% and less than 0.030%, surplus is iron and inevitable impurity, and using pearlite as principal phase, the hydrogen diffusion coefficient D in 300 DEG C of steel meets following (1) formula D≤2.5 × 10^‑7(cm²/ the second) ... (1).

Description

Steel wire wire rod and steel wire

Technical field

The present invention relates to the steel wire wire rod of the former material of the steel wire as high intensity for steel wire rope and PC steel wires etc. and Such steel wire.

Background technology

It is applied in the steel strand wires of alternating bending stress the hoisting line of Riata for elevator and crane etc. is this, rope strand Flexural fatigue turns into an important factor for design strength for determining rope and life-span.In recent years, along with the high speed of elevator With the miniaturization of crane, the lightweight demand of rope increases, it is desirable to realizes excellent high-strength of Flexural fatigue of this point Spend steel wire wire rod.The excellent high-tensile steel wires wire rod of other Flexural fatigue, as PC (Prestressed Concrete) former material of steel wire is also useful.In such steel wire wire rod, specifically, it is desirable to number of repetition will not occur For 10⁴~10⁵The secondary low-cycle fatigue just occurred.

As the technology of the characteristic for improving wire rod, up to now it is also proposed that having a variety of.It is for example, public in patent document 1 A kind of technology is provided with, it is by making fine precipitation BN systems field trash in steel, improve fatigue strength.

There is a kind of technology disclosed in patent document 2, it possesses the superfine steel of Wire Drawing pearlitic structrure by reducing Hydrogen amount in silk, so that via 10⁷The fatigue properties of the rotary bending fatigue test evaluation in individual cycle improve.

Prior art literature

Patent document

Patent document 1：Japanese Unexamined Patent Publication 2011-225990 publications

Patent document 2：Japanese Unexamined Patent Publication 11-256274 publications

Turn into the characteristic of problem in the technology of above-mentioned patent document 1, be that number of repetition is 10⁷It is secondary close to fatigue limit And the high cycle fatigue occurred, it is different from the mechanism of above-mentioned low-cycle fatigue.So it is exposed for a long time in extraneous air in steel wire rope In product, the friction between oxidation and rope strand due to skin section, fatigue cracking is caused easily to occur, and the hydrogen invaded in steel is led Cracking progress is caused, therefore material is broken under the life-span more much lower than fatigue limit.Therefore, it is necessary to countermeasure for hydrogen.

In addition, the fatigue properties that above-mentioned patent document 2 is considered are also high cycle fatigue, as steel wire rope and PC steel wires, In the case of having product as the hydrogen intrusion from the external world, because causing low cycle fatigue property to reduce from the hydrogen of outside intrusion, because This is only merely to reduce the hydrogen amount and insufficient in steel as so above-mentioned patent document 2.

The content of the invention

The present invention in view of above-mentioned such situation and formed, its object is to, there is provided a kind of low cycle fatigue property is excellent, makees For the useful steel wire wire rod of the former material of the steel wire of the high intensity of steel wire rope and PC steel wires etc. and such characteristic can be played Steel wire.

It can solve the problem that the steel wire wire rod of the invention of above-mentioned problem, it is characterised in that in terms of quality %, contain C respectively： 0.70~1.3%, Si：0.1~1.5%, Mn：0.1~1.5%, N：0.001~0.006%, Al：0.001~0.10%, Ti： 0.02~0.20%, B：0.0005~0.010%, P：More than 0% and below 0.030%, S：More than 0% and 0.030% Hereinafter, surplus is iron and inevitable impurity, using pearlite as principal phase, under the hydrogen diffusion coefficient D in the steel at 300 DEG C meets State (1) formula.

D≤2.5×10^-7(cm²/ the second) ... (1)

Further, so-called " using pearlite as principal phase ", mean 95 area % of metal structure above is pearlitic structrure.

The high-tensile steel wires wire rod of the present invention, it is also preferred that in terms of quality %, also contain as inferior：

(a)Cr：Higher than 0% and below 1.0% and V：At least one of higher than 0% and below 0.5%；

(b)Ni：Higher than 0% and below 0.5% and Nb：At least one of higher than 0% and below 0.5%；

(c)Co：Higher than 0% and below 1.0%；

(d)Mo：Higher than 0% and below 0.5% and Cu：At least one of higher than 0% and below 0.5%.

The present invention also includes being made up of the chemical composition of above-mentioned steel forming, and the hydrogen diffusion coefficient D in the steel at 300 DEG C expires Foot states the steel wire of (1) formula.

D≤2.5×10^-7(cm²/ the second) ... (1)

The effect of invention

According to the present invention, the hydrogen trap effect brought using the TiC of fine dispersion etc. Ti systems field trash, hinder in steel Hydrogen spreads, and its diffusion coefficient is reduced, so as to obtain the steel wire material of excellent in fatigue characteristics.Especially for 10⁴~10⁵It is secondary The low-cycle fatigue occurred under the alternate stress load of left and right, plays excellent characteristic.

Brief description of the drawings

Fig. 1 is the outline figure of the status of implementation of 4 repeated bend tests.

Embodiment

The present inventors, using pearlite as in the steel wire material as metal structure of principal phase, for left and right low-cycle fatigue The factor of performance has carried out adjusting Check with keen determination.The reduction of fatigue properties caused by hydrogen, it is due to that load alternate stress causes Hydrogen in steel makes the tissue of crack periphery brittle towards caused small crack diffusion in steel.Except being inhaled through manufacturing process It is attached to beyond the hydrogen in steel, similarly reduces fatigue properties from the hydrogen of external world's intrusion.Therefore, the hydrogen diffusion in steel is hindered, is subtracted The amount of the hydrogen of crack periphery is gathered in less, can improve fatigue properties.Specifically, spread the hydrogen in the steel at 300 DEG C Coefficient D is in 2.5 × 10^-7(cm²/ the second) below, then fatigue properties improve.

Hydrogen diffusion coefficient D is the physics value for depending on temperature, but spreads system in the present invention with the hydrogen in the steel at 300 DEG C Number D is as index.Its reason comes from the measuring method of hydrogen diffusion coefficient.In hydrogen diffusion coefficient D measurement, using making Sample heats up in measuring appliance, the method for the release profiles of the hydrogen obtained by analyzing, the low temperature parts of release profiles easily by To the influence of interference, it is unsuitable for accurately evaluating.This is because, the hydrogen of low temperature release is referred to as diffusivity hydrogen, at room temperature Diffusion can not be ignored, therefore can be affected according to the keeping state of the sample for measurement.Further, hydrogen diffusion coefficient D is preferred For 2.3 × 10^-7(cm²/ the second) below, more preferably 2.0 × 10^-7(cm²/ the second) below.

As the means for the diffusion for hindering hydrogen, make have the TiC of effect for adsorbing hydrogen etc. Ti systems field trash micro- in steel It is finely divided effective.

The steel wire wire rod of the present invention, its basic characteristic is set when suitable for steel wire etc. to play on the basis of, It is also required to rightly adjust its chemical composition composition.Its chemical composition composition is as follows.Further, " % " in chemical composition composition, It is " quality % ".

(C：0.70~1.3%)

Risings of the C for intensity is effective element, with the increase of C amounts, the wire rod (steel wire material) before cold working, and it is cold The intensity of steel wire after processing improves.Therefore, C amounts are set to more than 0.70%.C amounts are preferably more than 0.74%, more preferably More than 0.78%.But if C amounts are too surplus, proeutectoid cementite (it is following, sketch for " pro-eutectoid θ ") separate out, Wire Drawing In cause broken string.Therefore, C amounts are set to less than 1.3%.C amounts are preferably less than 1.2%, more preferably less than 1.1%.

(Si：0.1~1.5%)

Si has the function that to be used as deoxidier also have the function that to make the intensity of wire rod to improve in addition.In order that these are made With effectively playing, Si amounts are set to more than 0.1%.Si amounts are preferably more than 0.15%, more preferably more than 0.18%.It is another Aspect, if Si amounts are too surplus, deteriorate cold-drawn wire, cause the increase of outage.Therefore, Si amounts are set to less than 1.5%. Si amounts are preferably less than 1.4%, more preferably less than 1.3%.

(Mn：0.1~1.5%)

Mn is same with Si also to have deoxidation, but particularly has and fixed the S in steel as MnS, so as to carry The effect of Gao Gang toughness and ductility.In order that these effects effectively play, Mn amounts are more than 0.1%.Mn amounts are preferably More than 0.15%, more preferably more than 0.20%.But Mn is the element being easily segregated, if add superfluously, Mn segregations portion Hardenability exceedingly increase, it is possible to generate the over-cooling structure of martensite etc..Therefore, Mn amounts are set to less than 1.5%.Mn amounts Preferably less than 1.4%, more preferably less than 1.3%.

(N：0.001~0.006%)

N is combined chemically to form BN with the B in steel, loses B effect.In addition, the N of solid solution condition cause in wire drawing in response to The reduction of twisting property, then causes longitudinal crack caused by becoming timeliness when notable.In order to prevent these drawbacks, N amounts be 0.006% with Under.N amounts are preferably less than 0.005%, more preferably less than 0.004%.On the other hand, if on a small quantity, then TiN and AlN etc. Nitride make crystal grain miniaturization, have improve wire rod ductility effect.In order to play such effect, N amounts are More than 0.001%.N amounts are preferably more than 0.0015%, more preferably more than 0.0020%.

(Al：0.001~0.10%)

Al is effective deoxidant element.In addition, also having the effect that, form nitride as AlN and make crystal grain micro- Refinement.In order to effectively play such effect, Al amounts are more than 0.001%.Al amounts are preferably more than 0.002%, more preferably For more than 0.003%.On the other hand, if adding Al superfluously, Al is formed₂O₃Such oxide, increase broken string during wire drawing Add.From this viewpoint, Al amounts are less than 0.10%.Al amounts are preferably less than 0.09%, more preferably less than 0.08%.

(Ti：0.02~0.20%)

Carbide as Ti formation TiC, reduces Hydrogen diffusion coefficient, plays the work for improving the fatigue properties of steel wire With.In addition, the effect also having is, nitride as TiN is combined chemically to form with the N in steel, prevents that twisting is special caused by N The reduction of property.In order to effectively play these effects, Ti amounts are more than 0.02%.Ti amounts are preferably more than 0.03%, more preferably For more than 0.04%.On the other hand, if Ti amounts become superfluous, TiC and TiN etc. Ti systems field trash largely separate out, and make wire drawing When broken string increase.Therefore, Ti amounts are less than 0.20%.Ti amounts be preferably less than 0.15%, more preferably 0.10% with Under.

(B：0.0005~0.010%)

B have suppress to separate out in crystal boundary pro-eutectoid ferrite (it is following, sketch for " pro-eutectoid α ") effect, for tired The raising of labor characteristic is effective.In addition it is possible to which the effect expected is, by forming BN, the solid solution N fixed in steel, make twisting special Property improve.In order to effectively play B effect, B amounts are needed for more than 0.0005%.The lower limit of preferable B amounts is 0.0007% More than, more preferably more than 0.001%.On the other hand, if B amounts become superfluous, the Fe-B systems as the compound with Fe Compound, such as FeB₂Separate out, cause crackle during hot rolling, therefore B amounts need to be in less than 0.010%.B amounts are preferably Less than 0.008%, more preferably less than 0.006%.

(P：More than 0% and below 0.030%)

P is segregated in old austenite grain boundary and makes embrittlement of grain boundaries, reduces fatigue strength, therefore its content is more few more excellent Choosing.Therefore, P amounts are less than 0.030%.P amounts are preferably less than 0.025%, more preferably less than 0.020%.P amounts can also be 0%, but usually contain more than 0.001%.

(S：More than 0% and below 0.030%)

S is same with P, is segregated in old austenite grain boundary and makes embrittlement of grain boundaries, reduces fatigue strength, therefore its content is fewer It is more preferred.Therefore, S amounts are less than 0.030%.S amounts are preferably less than 0.025%, more preferably less than 0.020%.S amounts also may be used Think 0%, but usually contain more than 0.001%.

As described above, surplus is substantially iron to the basis of the wire rod of the present invention.But certainly allow because raw material, goods and materials, The situation of manufacturing equipment etc. and it is mixed inevitably impurity be included in steel in.

The wire rod of the present invention in addition, in order that the characteristic of intensity, toughness, ductility etc. further improves, further preferably basis Need, further containing following element etc.：

(c)Co：Higher than 0% and below 1.0%；

(Cr：Higher than 0%, less than 1.0% and V：Higher than 0%, at least one of less than 0.5%)

Cr and V is useful element in the intensity (tensile strength) for improving wire rod, can also be allowed to containing one kind or two Plant and be used in combination.

Particularly Cr has the sheet gap miniaturization for making pearlite, improves the effect of the intensity and toughness of wire rod.In order to Such effect is effectively played, Cr amounts are preferably more than 0.05%.Cr amounts are more preferably more than 0.10%, more preferably More than 0.15%.On the other hand, if Cr amounts are too surplus, hardenability improves, and the dangerous raising of over-cooling structure occurs in hot rolling, Therefore Cr amounts are preferably less than 1.0%.Cr amounts are more preferably less than 0.8%, more preferably less than 0.6%.

For V-arrangement into carbonitride, having makes the effect that the intensity of wire rod improves.In addition, it is same with Nb, after being separated out with AlN Remaining solid solution N form nitride, contribute to crystal grain miniaturization, in addition, also there is fixed solid solution N and to suppress timeliness crisp The effect of change.In order to effectively play such effect, V amounts are preferably more than 0.01%, more preferably more than 0.02%, enter one Step is preferably more than 0.03%.But V is the element of high price, even if add superfluously, its effect is also saturation, economically Cause to waste, therefore V amounts are preferably less than 0.5%, more preferably less than 0.4%, more preferably less than 0.2%.

(Ni：Higher than 0% and below 0.5% and Nb：At least one higher than 0% and below 0.5%)

Ni and Nb is useful element in the toughness for improving steel wire, can also be allowed to be used in combination containing one or two.

Particularly Ni is the element of the toughness of the steel wire after raising wire drawing.In order to effectively play such effect, Ni amounts Preferably more than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.But even if the superfluous additions of Ni, Its effect is also saturation, economically causes to waste.Therefore, Ni amounts are preferably less than 0.5%, more preferably less than 0.4%, are entered One step is preferably less than 0.3%.

Nb and Ti and Al is similarly formed nitride, makes crystal grain miniaturization, in addition to the toughness for contributing to steel wire improves, also Have by fixed solid solution N to suppress the effect of initial aging stage.In order to effectively play such effect, Nb amounts are preferably 0.01% More than, more preferably more than 0.03%, more preferably more than 0.05%.But Nb is the element of high price, even if superfluous ground Addition, its effect is also saturation, economically causes to waste, therefore Nb amounts preferably less than 0.5%, more preferably 0.4% with Under, more preferably less than 0.3%.

(Co：Higher than 0% and below 1.0%)

Co is particularly the generation that proeutectoid cementite is reduced when C amounts are high, and having makes tissue turn into uniform pearlite group Knit such effect.In order to effectively play this effect, Co amounts are preferably more than 0.05%, more preferably more than 0.1%, are entered One step is preferably more than 0.2%.But even if Co is added superfluously, its effect is also saturation, economically causes to waste.Cause This, Co amounts are preferably less than 1.0%, more preferably less than 0.8%, more preferably less than 0.6%.

(Mo：Higher than 0% and below 0.5% and Cu：At least one higher than 0% and below 0.5%)

Mo is the element for improving the corrosion resistance of steel wire.In order to effectively play such effect, Mo amounts are preferably More than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.But hold if Mo amounts are superfluous, during hot rolling Over-cooling structure easily occurs, also deteriorates ductility in addition.Therefore Mo amounts are preferably less than 0.5%, more preferably less than 0.4%, More preferably less than 0.3%.

Cu same with Mo is the element for improving the corrosion resistance of steel wire.In order to effectively play such effect, Cu amounts Preferably more than 0.05%, more preferably more than 0.08%, more preferably more than 0.10%.But if Cu amounts are superfluous, Reacted with S and be segregated CuS in crystal boundary portion, flaw occurs in wire rod manufacturing process.In order to avoid such influence, Cu amounts are preferred For less than 0.5%, more preferably less than 0.4%, more preferably less than 0.3%.

Mo and Cu can also be allowed to be used in combination containing one or two.

Next, illustrated for the steel wire that can manufacture the present invention with the method for wire rod.

Wire rod before cold-drawn wire, melting, split rolling method are carried out typically by the steel for appropriately controlling chemical composition And hot rolling, manufactured further according to progress patenting processing is needed.Meet on one side important document given to this invention (metal structure, Hydrogen diffusion coefficient) while when manufacturing the wire rod of the present invention, it is important that Ti content is appropriately controlled in above-mentioned scope And then the precipitation movement of suitable control TiC etc. Ti systems field trash.

First, in split rolling method, slab is preferably heated to more than 1200 DEG C, separated out when decomposing casting thick TiC.If heating-up temperature is lower than 1200 DEG C, the thick TiC of remaining in wire rod, it is impossible to hydrogen diffusion coefficient is fully reduced, therefore it is tired Labor intensity decreases.The heating-up temperature is more preferably more than 1250 DEG C, more preferably more than 1300 DEG C.But Ruo Jiarewen Height is spent, then the melting of wire rod occurs, therefore is normally set to 1400 DEG C or so.

When then carrying out hot rolling, it is preferably heated to after more than 1000 DEG C, makes the rate of straining of final 4 passages of rolling For 0.5 second^-1More than, make crystal grain miniaturization by dynamically recrystallizing, and separate out fine TiC.If above-mentioned rate of straining Than 0.5 second^-1It is small, then it can not make TiC fully miniaturizations, it is impossible to fully reduce hydrogen diffusion coefficient D.At this moment rate of straining is more excellent Elect as 0.8 second^-1More than, more preferably 1.0 seconds^-1More than.But the problem of slave unit load, considers, above-mentioned rate of straining Preferably generally 5 seconds^-1Below.Further, rate of straining V ε, using being reached the standard grade from final passage as the roller in front of 4 passages One it is mixed before basal area S₀(m²), and pass through the basal area S after final passage₄(m²), and total passage time of 4 passages (rolling time) t (second), represented by following (2) formulas.

V ε={ ln (S0/S₄)}/t…(2)

It is preferably sufficiently cool by water cooling after hot rolling, by the mounting temperature control of the Laying head of rolled stock (wire rod) 800 ~1000 DEG C.If loading temperature is higher than 1000 DEG C, in the cooling on conveyer after loading, TiC is possible to coarsening.Mounting Temperature is more preferably less than 980 DEG C, more preferably less than 950 DEG C.In addition, when mounting temperature is less than 800 DEG C, the change of wire rod Form drag increases, for example, it is possible to which the mounting for occurring to wind etc. on Laying head is bad.Therefore mounting temperature is preferably 800 More than DEG C.Mounting temperature is more preferably more than 820 DEG C, more preferably more than 850 DEG C.

After mounting, wire rod is cooled down on coolconveyer, pearlitic transformation is made in cooling, but preferably to pearly-lustre body phase Become the average cooling rate started and carry out chilling into more than 5 DEG C/sec.If average cooling rate at this moment is slow, TiC is easily thick Bigization, hydrogen diffusion coefficient are possible to become big.In addition, if average cooling rate is smaller than 5 DEG C/sec, locally has and be referred to as slightly Pearlite (コーズパーライト) the extremely thick tissue of sheet gap separate out, can also reduce stringiness.Further, in pearl The beginning of body of light phase transformation, the temperature of wire rod is measured, the point (flex point) of cooling curve change is tried to achieve according to phase transformation heat release.This is flat Equal cooling velocity is more preferably more than 10 DEG C/sec, more preferably more than 15 DEG C/sec.Average cooling rate it is preferable on It is limited to less than 100 DEG C/sec, more preferably less than 50 DEG C/sec.

The wire rod obtained as described so, directly it can be used through Wire Drawing (cold working) as steel wire, but can also Implement patenting processing before Wire Drawing.Handled by the patenting before Wire Drawing as implementation, it is possible to increase wire rod Intensity, and reduce strength variance.

In addition, be contemplated to during steel wire as manufactured minor diameter Wire Drawing degree it is big when, carried out by rolled stock it is certain Implement patenting processing after degree wire drawing, wire rod tissue is revert to unprocessed pearlitic structrure and then is carried out wire drawing and add Work is also useful.At this moment, if handling the TiC for also ensuring that fine precipitation by reheating, handled by general patenting Also the low states of hydrogen diffusion coefficient D can be kept.

Heating-up temperature (following, the temperature is referred to as into " relation reheating temperature ") when implementing patenting processing is preferably 900~ 1000 DEG C or so, more preferably more than 920 DEG C and less than 980 DEG C.From non-solid solution carbides remaining is prevented, make the complete Ovshinsky of tissue From the viewpoint of body, relation reheating temperature is preferably more than 900 DEG C, if but excessively high temperature, TiC coarsenings and hydrogen diffusion coefficient D increases.In addition, the keeping temperature of patenting processing is preferably 530~600 DEG C or so, more preferably more than 550 DEG C and 580 DEG C Below.

The wire rod of the present invention, because the hydrogen diffusion coefficient D in steel is fully reduced, cold working has been carried out to it Steel wire, and it is all or part of used the steel wire rope of the steel wire and the product of PC steel wires etc., than usual product excellent in fatigue characteristics.

The application is based on Japan's patent application 2014-136223 CLAIM OF PRIORITYs filed in 1 day July in 2014 Interests.The full content for the specification that Japan's patent application the 2014-136223rd, in this application be used for refer to and Quote.

Embodiment

Hereinafter, enumerate embodiment and further illustrate the present invention.The present invention is not limited by the examples below, and can accorded with Implementation can certainly suitably be changed by closing the scope of objective foregoing, described later, and these are all contained in the technology model of the present invention In enclosing.

The steel ingot formed for the chemical composition shown in table 1 below, cogging, hot rolling are carried out with the condition shown in table 2 below And be processed into wire rod coiled material, a part again with shown in Table 3 below and condition carry out patenting processing.With rolling shown in table 2 below Line footpath processed and the lead shown in Table 3 below are quenched the different coiled material of line footpath, represent that folder is heat-treated every middle wire drawing.

[table 1]

[table 2]

[table 3]

Using the sample extracted from the wire rod before finish draw silk, according to following methods, implement tension test, metal structure Evaluation, hydrogen diffusion coefficient D measurement.

(tension test)

The tensile strength TS (Tensile Strength) of the sample of extraction, according to JIS Z 2241 (2011) measurements.Steel Silk makes 8, averages.Its result is shown in table 4 below.

(evaluation of metal structure)

It is the cross section with the sample of observation by light microscope extraction on metal structure.Further, in the gold of table 4 below In the project for belonging to tissue, it is shown as " P ", represents pearlitic structrure more than 95 area %, i.e. pearlite is principal phase.In addition, It is shown as " P+ α " and " P+ θ's ", expression is such as undertissue：Pearlitic structrure is less than 95 area %, except pearlitic structrure with Outside, ferrite (α) and cementite (θ) more than 5 area % are also mixed with.

(hydrogen diffusion coefficient D measurement)

Carry out oozing hydrogen until saturation state, hydrogen release profiles are obtained by the analysis that heats up for the sample of extraction.Heating speed Spend for 12 DEG C/sec, the discharging amount of hydrogen is measured with atmospheric pressure ionization mass spectrometry analysis meter.Ooze in hydrogen condition, electrolyte uses H₂SO₄Water Solution (pH3)+KSCN0.01mol/L, with current density 5mA/cm²Permeate within 48 hours.Further, in the sample after infiltration, In order to strongly prevent the discrete of hydrogen, taken care of in liquid nitrogen until measurement.

For resulting hydrogen release profiles, approximation is uniformly distributed in sample with hydrogen, specimen shape is assumed to unlimited circle Post, it is fitted using diffusion coefficient as parameter through the hydrogen release profiles obtained by numerical computations, thus tries to achieve hydrogen diffusion system Number D.As a result it is shown in table 4 below.Further, in order that Infinite Cylinder is approximate effectively, specimen length is more than 5 times of diameter. In addition at this moment, the releasing peak value of hydrogen used in fitting, more than 200 DEG C of peak value of peak temperature is used.200 DEG C appear below The peak value of low temperature is referred to as diffusivity hydrogen, it is contemplated that diffusion at room temperature such as is also released at the influence of interference, is not used in diffusion coefficient Evaluation.According to so obtained temperature and the correlation curve of diffusion coefficient, the diffusion coefficient tried to achieve at 300 DEG C spreads as hydrogen Coefficient D.

Then, Wire Drawing is carried out to resulting wire rod coiled material and makes steel wire (steel wire), implement tension test, twisting The evaluation of characteristic, the evaluation of fatigue properties, hydrogen diffusion coefficient D measurement.In table 5 below, show that section during Wire Drawing is received The line footpath of shrinkage and the steel wire obtained by Wire Drawing.

(tension test)

The tensile strength TS and yield point YP (Yield Point) of steel wire are according to JIS Z 2241 (2011) measurements.Steel wire 8 are made, is averaged.As a result it is shown in table 5 below.In addition, the value that tensile strength TS is multiplied by 0.45 is shown in following tables 5。

(evaluation of twisting property)

On twisting property, based on twisting experiment is carried out, commented to the twisting value (fracture twist number) required for being broken Valency.Twisting value in table 5 below is the average value of N=5 roots.At this moment, reverse speed is 52 beats/min, tension force 500gf (4.9N).Further, twisting value is that distance between chuck (experiment line length) is converted into line footpath d 100 times (100d) and is allowed to standard Change.In addition, being observed by section, normal section and longitudinal crack are differentiated, even if having 1 longitudinal crack occurs in 5, in aftermentioned table It is " having longitudinal crack " also to be described in 5.

(evaluations of fatigue properties)

On fatigue properties, by the use of the fixture as 4 dot points, implement four-point bending fatigue test repeatedly and commented Valency.In Fig. 1,1 test film (wire rod) is represented, 2 represent to apply the direction of alternate stress, and zero represents supporting-point.Experiment is with folk prescription Bend (piece song げ) to carry out, the difference of maximum stress and minimum stress is defined as stress amplitude.10 are carried out with various stress amplitudes The repeated flex of ten thousand times, the judgement of complete unbroken (broken string) is qualified in the experiment of N=3 roots, even if there is 1 to be broken Also it is determined as unqualified.It is determined as the maximum stress amplitude of qualified sample, is defined as 100,000 fatigue strength.100000 times tired Labor intensity is shown in table 5 below.Further, stress wave is sine wave, frequency 10Hz.

(hydrogen diffusion coefficient D measurement)

For steel wire, as reference value, with condition same as described above, hydrogen diffusion coefficient D is also tried to achieve.As a result it is shown in down State in table 5.

[table 4]

[table 5]

By these as a result, it is possible to be investigated as follows.

No.1~3,9~20, chemical composition composition, metal structure (area occupation ratio of pearlite), hydrogen diffusion system are tested first Number D is in scope given to this invention, therefore has been obtained higher than " the piano wire B classes " described in JIS G 3522 (1991) Tensile strength (in specification, such as line footpath is 7.0mm, 1620~1770MPa), and can obtain reaching strong higher than tension Spend the steel wire (steel wire) of TS 0.45 times of fatigue strength.

In contrast, experiment No.4~8,21~26, are the examples for being unsatisfactory for a certain important document of the present invention.Wherein test The low therefore thick TiC of heating-up temperature during its split rolling method of No.4 is separated out, and hydrogen diffusion coefficient D becomes big, and fatigue strength reduces.

No.5 is tested, because the rate of straining of final 4 passage during hot rolling is small, thick TiC is separated out, hydrogen diffusion system Number D becomes big, and fatigue strength reduces.

No.6 is tested, because the mounting temperature after hot rolling is low, bad generation is loaded and cannot get sample.

Mounting temperature after its hot rolling of experiment No.7 is high, and cooling velocity after its rolling of experiment No.8 is slow in addition, therefore TiC Coarsening and hydrogen diffusion coefficient D become big, and fatigue strength reduces.

Experiment No.21 is the example for the steel grade P for having used C amounts few, turns into the mixed phase tissue of ferrite and pearlite, tension Intensity and twisting property are low, and fatigue strength also reduces.

Experiment No.22 is the example for the steel grade Q for having used C amounts more, and substantial amounts of proeutectoid cementite separates out, therefore in wire drawing Break.

Experiment No.23 is the example for the steel grade R for having used Ti amounts few, and TiC amounts are few, and hydrogen diffusion coefficient D is big, fatigue strength reduction It is low.

Experiment No.24 is the example for having used the steel grade S more than Ti amounts, substantial amounts of Ti systems Inclusion Precipitation and sent out in wire drawing Raw broken string.

Experiment No.25 is the example for the steel grade T for having used B amounts more, occurs to break and cannot get sample during hot rolling.

Experiment No.26 is the example for the steel grade U for having used B amounts few, and twisting property and fatigue strength reduce.Other hydrogen diffusion Coefficient D also becomes big.

Claims

1. a kind of steel wire wire rod, wherein, in terms of quality %, it is made up of following component：

C：0.70~1.3%,

Si：0.1~1.5%,

Mn：0.1~1.5%,

N：0.001~0.006%,

Al：0.001~0.10%,

Ti：0.02~0.20%,

B：0.0005~0.010%,

P：More than 0% and less than 0.030%,

S：More than 0% and less than 0.030%,

Surplus：Iron and inevitable impurity,

95 area % of metal structure above is pearlitic structrure,

Hydrogen diffusion coefficient D in steel at 300 DEG C meets following (1),

D≤2.5×10^-7cm²/ the second ... (1).

2. a kind of steel wire wire rod, wherein, in terms of quality %,

It is made up of following component：

C：0.70~1.3%,

Si：0.1~1.5%,

Mn：0.1~1.5%,

N：0.001~0.006%,

Al：0.001~0.10%,

Ti：0.02~0.20%,

B：0.0005~0.010%,

P：More than 0% and less than 0.030%,

S：More than 0% and less than 0.030%,

Selected from Cr：Higher than 0% and below 1.0%, V：Higher than 0% and below 0.5%, Ni：Higher than 0% and 0.5% with Under, Nb：Higher than 0% and below 0.5%, Co：Higher than 0% and below 1.0%, Mo：Higher than 0% and below 0.5% and Cu：At least one of higher than 0% and below 0.5%,

Surplus：Iron and inevitable impurity,

95 area % of metal structure above is pearlitic structrure,

Hydrogen diffusion coefficient D in steel at 300 DEG C meets following (1),

D≤2.5×10^-7cm²/ the second ... (1).

3. a kind of steel wire, it is made up of the chemical composition of the steel described in claim 1 or 2 and formed, and the hydrogen in the steel at 300 DEG C expands Dissipate coefficient D and meet following (1) formulas,

D≤2.5×10^-7cm²/ the second ... (1).